Manchester United's history is replete with famous performances in Europe but the euphoric supporters who chanted "we want eight" as Roma suffered the ultimate humiliation might easily argue that they witnessed the finest display of them all. The Old Trafford scoreboard will provide photographs for years to come on a night when Sir Alex Ferguson's side subjected the Italian side to a defeat guaranteed to reverberate around Europe.

United were rampant, evincing all the values so ingrained in a club who demand free-flowing, attack-minded football. And last night it produced the biggest winning margin in a Champions League knock-out round game, Roma's heaviest defeat in Europe and United's biggest win in Europe since a 7-1 victory over Waterford in the first round of the European Cup in 1968-69, when they were the defending champions. It was also the biggest victory in a quarter-final match since Real Madrid beat Sevilla 8-0 in 1957-58.

United's traditions were laid down before then, at the start of the Matt Busby's era, and although the current generation have yet to reach those heights, this remarkable victory suggests that their ambitions have no limits.

Cristiano Ronaldo is playing with the world as well as the ball at his feet, his ability to turn defenders, score with ease and also provide entertainment supporting Wayne Rooney's assertion that "he is the best player in the world, by far".

He is unplayable in this form and the winners of tonight's quarter-final between Bayern Munich and Milan would be advised to keep footage of the winger away from their players. Ronaldo was not the only outstanding performer, but no one carries United's threat with the same intoxicating presence.

His two goals took him to 20 for the season, a remarkable contribution for a player expected to get chalk on his heels. The wing was where he picked up possession prior to United's first goal before dropping his shoulder and delivering the square pass that Michael Carrick, revelling in the freedom Roma afforded, collected and promptly dispatched past Doni. Carrick would later add a brilliant second.

Ronaldo was far from alone in tormenting Roma, though, with Ryan Giggs contributing directly to four of the seven goals. The Welshman no longer leaves players trailing but his brain is sharper than most, buying the space that his legs used to create. Ronaldo twice profited from the Welshman's artistry, drilling home from the edge of the area before applying a more routine finish after the interval.

How Ferguson could afford to smile. Only 24 hours earlier he had been informed that never during his reign had United managed to overturn a first-leg deficit in this competition. Borussia Dortmund, Bayern Munich, Real Madrid, Porto and Milan had all progressed at his expense after going into the second leg ahead. Roma never looked like adding their name to that list, though, with Luciano Spalletti's side crumbling.

Passes were exchanged with almost telepathic understanding, attacks constructed at breathtaking pace and goals converted with unforgiving ruthlessness. It was as if Roma were being punished for United's defeat at Portsmouth on Saturday, one that had done so much to undermine their title challenge. No one, not even Ferguson, could have predicted that United would approach a tie that demanded caution with such gusto.

This match had appeared to present a conundrum for the manager, with keeping a clean sheet seen as imperative. Nothing was further from the truth as United could afford to not only concede when Daniele de Rossi pilfered a consolation, but also to play the closing stages with 10 men. Ferguson had already introduced three substitutes when Rio Ferdinand departed.

Italian sides are synonymous with sound defensive foundations but Roma had the stability of a straw house here. Their midfield was hopelessly overrun, Carrick, Ronaldo and Giggs linking seamlessly to wreak havoc time and again. It is too late for Roma to learn lessons but should Milan prevail this evening, their Italian rivals will surely take heed. Conceding space to United is almost as big a crime as suggesting Ferguson is close to his sell-by date.

The United manager, reported to be on the brink when his side exited at the group stage of this competition last season after a chastening defeat at Benfica, remains on course to repeat the treble that brought such acclaim eight years ago.

Ferguson predicted that scoring once might be enough against Roma but his players seemingly decided defence was the best form of attack. It was an approach that yielded unprecedented reward, with the United's fans' delirium only momentarily quelled by news that Chelsea had won in Valencia. It was a truly impressive result for the London club but United's manager could be forgiven for believing they would not be capable of the damage United inflicted here.